1. Field of the Invention
The present invention relates to a transitory or temporary storage vessel for highly-radioactive waste. The transitory storage vessel incorporates containers for the receipt of the waste, and a cooling system for the discharge of the heat which is produced during the storage of the waste. The cooling system incorporates a cooling air duct, as well as a coolant circuit for a coolant which is conveyed in a closed circuit between coolant conduits, which conduct away heat generated in the storage space, and a heat sink arranged externally of the storage space.
2. Discussion of the Prior Art
Transitory storages vessels serve for the repository of processed highly-radioactive wastes until their reuse or until their introduction into a permanent repository. Such wastes are produced during the reconditioning of nuclear fuel elements subsequent to their use in a nuclear reactor. However, radioactive wastes must also be removed during the production of radioactive fluorescent substances or from isotope laboratories.
The highly-radioactive materials are concentrated prior to their storage. The materials are embedded or introduced into suitable carrier substances, or as a calcinate, which is obtained during the reconditioning. Suitable, for example, as a carrier substance is borosilicate glass. Thus, it is known to encase the highly-radioactive materials within non-corrosive, gastight steel containers. The highly-radioactive waste is to be conveyed into repositories subsequent to its encapsulation, which act in a radiation-screening manner. In addition thereto, provision must be made to remove the heat which is produced during storage as a result of the decay of the radioactive material, which is designated as "decaying heat", so that the containers which contain the radioactive waste, and under certain circumstances, the carrier substance which contains the radioactive waste, is itself not overheated by the developed heat. Consequently, the repository is cooled.
U.S. Pat. No. 3,866,424 describes a storage for radioactive waste wherein waste capsules containing the waste are introduced into heater tubes which are filled with a refluxing coolant and, in addition thereto, traverse a cooling bath. The coolant of the cooling bath is conducted, within a primary cooling circuit, through a heat exchanger which is arranged externally of the storage space. In the heat exchanger, the coolant rejects the heat carried along therewith to a working medium circuit which includes a compressor and turbine. In order to provide for protection against overheating and redundancy of the system, auxiliary secondary cooling devices are provided for and cooling bath itself, and also for the coolant liquid which is located in the heater tubes. The activity in the function and safety of this known cooling system depends, above all, upon the cooling of the waste itself by means of the coolant liquid in the heater tubes. Thus, when leakages are encountered within the heater tubes, there must be expected considerable disturbances.
Another storage vessel for radioactive waste has become known from U.S. Pat. No. 3,911,684. In this storage vessel, the storage capsules, which are filled with waste, have cooling air circulated thereabout. The cooling air is conveyed in a closed circuit for economic utilization whereby, for example, the heat which is carried along can be transferred by means of a heat exchanger to a work medium of a work medium circuit which includes a turbine. Any redundancy of the system is not only achieved through the arrangement of further heat exchangers in the circuit of the cooling air, but provision is also made that, in the case of any disturbance, by means of the employment of natural convection, cooling air can flow into the storage space. It is disadvantageous that the cooling air can be conveyed within the storage space only with such difficulty so as to prevent any localized overheating. Upon the occurrence of a fracture in a storage tube, the highly-radioactive waste will then find itself directly in the cooling air flow.